Anionic polymerization of conjugated dienes modified with alkyltetrahydrofurfuryl ethers

ABSTRACT

It has been unexpectedly discovered that various compounds, such as alkyl tetrahydrofurfuryl ethers, can be used to modify anionic polymerizations of conjugated diene monomers. These modifiers can be used to polymerize isoprene monomer into high 3,4-polyisoprene at excellent polymerization rates. This is in contrast to the modifiers such as tetramethylethylene diamine which are typically used to modify such polymerizations. This invention more specifically discloses a process for the synthesis of 3,4-polyisoprene which comprises polymerizing isoprene monomer in an organic solvent in the presence of a catalyst system which is comprised of (a) a lithium initiator and (b) ethyltetrahydrofurfuryl ether.

BACKGROUND OF THE INVENTION

It is important for polydienes which are used in many applications tohave high vinyl contents. For example, 3,4-polyisoprene can be used intire tread compounds to improve tire performance characteristics, suchas traction. Polar modifiers are commonly used in the preparation ofsynthetic polydiene rubbers which are prepared utilizing lithiumcatalyst systems in order to increase their vinyl content. Ethers andtertiary amines which act as Lewis bases are commonly used as modifiers.For instance, U.S. Pat. No. 4,022,959 indicates that diethyl ether,di-n-propyl ether, diisopropyl ether, di-n-butyl ether, tetrahydrofuran,dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether,diethylene glycol dimethyl ether, diethylene glycol diethyl ether,triethylene glycol dimethyl ether, trimethylamine, triethylamine,N,N,N',N'-tetramethylethylenediamine, N-methyl morpholine, N-ethylmorpholine, and N-phenyl morpholine can be used as modifiers. U.S. Pat.No. 4,696,986 describes the use of 1,2,3-trialkoxybenzenes and1,2,4-trialkoxybenzenes as modifiers. The vinyl group content ofpolydienes prepared utilizing Lewis bases as modifiers depends upon thetype and amount of Lewis base employed as well as the polymerizationtemperature utilized. For example, if a higher polymerizationtemperature is employed, a polymer with a lower vinyl group content isobtained (see A.W. Langer; A. Chem. Soc. Div. Polymer Chem. Reprints;Vol. 7 (1), 132 [1966]). For this reason it is difficult to synthesizepolymers having high vinyl contents at high polymerization temperaturesutilizing typical Lewis base modifiers.

Higher temperatures generally promote a faster rate of polymerization.Accordingly, it is desirable to utilize moderately high temperatures incommercial polymerizations in order to maximize throughputs. However, ithas traditionally been difficult to prepare polymers having high vinylcontents at temperatures which are high enough to attain maximumpolymerization rates while utilizing conventional Lewis bases asmodifiers.

SUMMARY OF THE INVENTION

It has been determined that compounds having the following structuralformulae can be used as modifiers in the synthesis of polydienes:##STR1## wherein n represents an integer within the range of 3 to 6, andwherein R, R¹, and R² can be the same or different and represent alkylgroups containing from 1 to 10 carbon atoms, aryl groups containing from6 to 10 carbon atoms, or hydrogen atoms.

Such polydienes are prepared utilizing initiators which are based onlithium, sodium, potassium, magnesium, or barium. As a general rule,organolithium compounds are preferred. The modifiers of this inventionare very strong modifiers; the use of which can result in the formationof polymers with very high vinyl contents.

The modifiers of this invention remain stable at conventionalpolymerization temperatures and lead to the formation of polymers havinghigh vinyl contents at such temperatures. Accordingly, they can be usedto promote the formation of high vinyl polymers at temperatures whichare high enough to promote very fast polymerization rates.

The present invention specifically discloses a process for the synthesisof a rubbery polymer which comprises polymerizing (1) from about 50weight percent to 100 weight percent conjugated diene monomers and (2)from 0 weight percent to about 50 weight percent monomers which arecopolymerizable or terpolymerized with said conjugated diene monomers,in an inert organic solvent in the presence of a catalyst system whichis comprised of (a) an initiator selected from the group consisting oforganolithium compounds, organosodium compounds, organomagnesiumcompounds, and organobarium compounds and (b) a modifier selected fromthe group consisting of: ##STR2## wherein n represents an integer withinthe range of 3 to 6, and wherein R, R¹, and R² can be the same ordifferent and represent alkyl groups containing from 1 to 10 carbonatoms, aryl groups containing from 6 to 10 carbon atoms, or hydrogenatoms.

The subject invention also discloses a catalyst system which isparticularly useful in the anionic polymerization of conjugated dienemonomers into polymers which is comprised of (a) an initiator which isselected from the group consisting of organolithium compounds,organosodium compounds, organopotassium compounds, organomagnesiumcompounds, and organobarium compounds and (b) a modifier selected fromthe group consisting of: ##STR3## wherein n represents an integer withinthe range of 3 to 6, and wherein R, R¹, and R² can be the same ordifferent and represent alkyl groups containing from 1 to 10 carbonatoms, aryl groups containing from 6 to 10 carbon atoms, or hydrogenatoms.

DETAILED DESCRIPTION OF THE INVENTION

The polymers which can be prepared utilizing the modifiers of thepresent invention are normally organolithium-initiated, vinyl groupcontaining polymers of at least one diolefin monomer which are generallyrubbery (elastomeric) polymers. The diolefin monomers utilized in thepreparation of such polymers normally contain from 4 to 12 carbon atomswith those containing from 4 to 8 carbon atoms being more commonlyutilized. The diolefin monomers used in such polymers are normallyconjugated diolefins.

The conjugated diolefin monomers which are utilized in the synthesis ofsuch polymers generally contain from 4 to 12 carbon atoms. Thosecontaining from 4 to 8 carbon atoms are generally preferred forcommercial purposes. For similar reasons, 1,3-butadiene and isoprene arethe most commonly utilized conjugated diolefin monomers. Some additionalconjugated diolefin monomers that can be utilized include2,3-dimethyl-1,3-butadiene, piperylene, 3-butyl-1,3-octadiene,2-phenyl-1,3-butadiene, and the like, alone or in admixture.

Feed stocks which are comprised of one or more conjugated diolefinmonomers in admixture with other low molecular weight hydrocarbons canbe utilized. Such admixtures, termed low concentration diene streams,are obtainable from a variety of refinery product streams, such asnaptha-cracking operations or can be intentionally blended compositions.Some typical examples of low molecular weight hydrocarbons which can beadmixed with diolefin monomers, such as 1,3-butadiene, in thepolymerization feed include propane, propylene, isobutane, n-butane,1-butene, isobutylene, trans-2-butene, cis-2-butene, vinylacetylene,cyclohexane, ethylene, propylene, and the like.

Copolymers of one or more diolefin monomers having high vinyl contentscan also be prepared utilizing the modifiers of the present invention.For instance, copolymers of isoprene and butadiene having high vinylcontents can be synthesized.

Polydiene rubbers having high vinyl contents which are copolymers orterpolymers of diolefin monomers with one or more other ethylenicallyunsaturated monomers which are copolymerizable with diolefin monomerscan also be prepared utilizing the modifiers of this invention. Somerepresentative examples of ethylenically unsaturated monomers that canpotentially be synthesized into such high vinyl polymers include alkylacrylates, such as methyl acrylate, ethyl acrylate, butyl acrylate,methyl methacrylate and the like; vinylidene monomers having one or moreterminal CH₂ -CH-groups; vinyl aromatics such as styrene,α-methylstyrene, bromostyrene, chlorostyrene, fluorostyrene and thelike; α-olefins such as ethylene, propylene, 1-butene, and the like;vinyl halides, such as vinylbromide, chloroethane (vinylchloride),vinylfluoride, vinyliodide, 1,2-dibromoethene, 1,1-dichloroethene(vinylidene chloride), 1,2-dichloroethene, and the like; vinyl esters,such as vinyl acetate; α,β-olefinically unsaturated nitriles, such asacrylonitrile and methacrylonitrile; α,β-olefinically unsaturatedamides, such as acrylamide, N-methyl acrylamide, N,N-dimethylacrylamide,methacrylamide and the like.

Polydiene rubbers which are copolymers of one or more diene monomerswith one or more other ethylenically unsaturated monomers will normallycontain from about 50 weight percent to about 99 weight percent dienemonomers and from about 1 weight percent to about 50 weight percent ofthe other ethylenically unsaturated monomers in addition to the dienemonomers. For example, copolymers of diene monomers with vinylaromaticmonomers, such as styrene-butadiene rubber (SBR) which contain from 50to 95 weight percent diene monomers and from 5 to 50 weight percentvinylaromatic monomers are useful in many applications.

Vinyl aromatic monomers are probably the most important group ofethylenically unsaturated monomers which are commonly incorporated intopolydienes. Such vinyl aromatic monomers are, of course, selected so asto be copolymerizable with the diolefin monomers being utilized.Generally, any vinyl aromatic monomer which is known to polymerize withorganolithium initiators can be used. Such vinyl aromatic monomerstypically contain from 8 to 20 carbon atoms. Usually the vinyl aromaticmonomer will contain from 8 to 14 carbon atoms. The most widely usedvinyl aromatic monomer is styrene. Some examples of vinyl aromaticmonomers that can be utilized include 1-vinylnaphthalene,2-vinylnaphthalene, 3-methylstyrene, 4-propylstyrene,4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene,4-(phenylbutyl)styrene, and the like.

The relative amount of conjugated diene or dienes and monovinyl aromaticcompound or compounds employed can vary over a wide range. In preparingrubbery polymers, the proportion of the conjugated diene versus themonovinyl-substituted aromatic compound should be sufficient so as toresult in a substantially rubbery or elastomeric copolymer product.There is no sharp break point as to the amount of conjugated dieneversus monovinyl-substituted aromatic compound that confers rubbery orelastomeric properties on the resulting copolymer, though in general atleast 50 parts by weight of conjugated diene are required on anexemplary basis. Thus, for a rubbery copolymer, as is preferred inaccordance with this invention, the weight ratio of conjugated diene tomonovinyl aromatic compound in the monomer charge would be in the rangeof about 50:50 to 95:5. Of course, mixtures of conjugated dienes as wellas mixtures of monovinyl-substituted aromatic compounds can be utilized.

The polymerizations of the present invention which are carried out in ahydrocarbon solvent which can be one or more aromatic, paraffinic, orcycloparaffinic compounds. These solvents will normally contain from 4to 10 carbon atoms per molecule and will be liquids under the conditionsof the polymerization. Some representative examples of suitable organicsolvents include pentane, isooctane, cyclohexane, normal hexane,benzene, toluene, xylene, ethylbenzene, and the like, alone or inadmixture. The modifiers of this invention are also useful in bulkpolymerizations which are initiated with lithium catalyst systems.

In solution polymerizations which utilize the modifiers of thisinvention, there will normally be from 5 to 35 weight percent monomersin the polymerization medium. Such polymerization mediums are, ofcourse, comprised of an organic solvent, monomers, an organolithiuminitiator, and the modifier. In most cases it will be preferred for thepolymerization medium to contain from 10 to 30 weight percent monomers.It is generally more preferred for the polymerization medium to contain20 to 25 weight percent monomers.

The organolithium initiators employed in the process of this inventioninclude the monofunctional and multifunctional types known forpolymerizing the monomers described herein. The multifunctionalorganolithium initiators can be either specific organolithium compoundsor can be multifunctional types which are not necessarily specificcompounds but rather represent reproducible compositions of regulablefunctionality.

The amount of organolithium initiator utilized will vary with themonomers being polymerized and with the molecular weight that is desiredfor the polymer being synthesized. However, as a general rule from 0.01to 1 phm to (parts per 100 parts by weight of monomer) of anorganolithium initiator will be utilized. In most cases, from 0.01 to0.1 phm of an organolithium initiator will be utilized with it beingpreferred to utilize 0.025 to 0.07 phm of the organolithium initiator.

The choice of initiator can be governed by the degree of branching andthe degree of elasticity desired for the polymer, the nature of thefeedstock, and the like. With regard to the feedstock employed as thesource of conjugated diene, for example, the multifunctional initiatortypes generally are preferred when a low concentration diene stream isat least a portion of the feedstock, since some components present inthe unpurified low concentration diene stream may tend to react withcarbon lithium bonds to deactivate initiator activity, thusnecessitating the presence of sufficient lithium functionality in theinitiator so as to override such effects.

The multifunctional initiators which can be used include those preparedby reacting an organomonolithium compounded with a multivinylphosphineor with a multivinylsilane, such as reaction preferably being conductedin an inert diluent such as a hydrocarbon or a mixture of a hydrocarbonand a polar organic compound. The reaction between the multivinylsilaneor multivinylphosphine and the organomonolithium compound can result ina precipitate which can be solubilized if desired, by adding asolubilizing monomer such as a conjugated diene or monovinyl aromaticcompound, after reaction of the primary components. Alternatively, thereaction can be conducted in the presence of a minor amount of thesolubilizing monomer. The relative amounts of the organomonolithiumcompound and the multivinylsilane or the multivinylphosphine preferablyshould be in the range of about 0.33 to 4 moles of organomonolithiumcompound per mole of vinyl groups present in the multivinylsilane ormultivinylphosphine employed. It should be noted that suchmultifunctional initiators are commonly used as mixtures of compoundsrather than as specific individual compounds.

Exemplary organomonolithium compounds include ethyllithium,isopropyllithium, n-butyllithium, sec-butyllithium, tert-octyllithium,n-eicosyllithium, phenyllithium, 2-naphthyllithium,4-butylphenyllithium, 4-tolyllithium, 4-phenylbutyllithium,cyclohexyllithium, and the like.

Exemplary multivinylsilane compounds include tetravinylsilane,methyltrivinylsilane, diethyldivinylsilane, di-n-dodecyldivinylsilane,cyclohexyltrivinylsilane, phenyltrivinylsilane, benzyltrivinylsilane,(3-ethylcyclohexyl) (3-n-butylphenyl)divinylsilane, and the like.

Examplary multivinylphosphine compounds include trivinylphosphine,methyldivinylphosphine, dodecyldivinylphosphine, phenyldivinylphosphine,cyclooctyldivinylphosphine, and the like.

Other multifunctional polymerization initiators can be prepared byutilizing an organomonolithium compound, further together with amultivinylaromatic compound and either a conjugated diene ormonovinylaromatic compound or both. These ingredients can be chargedinitially, usually in the presence of a hydrocarbon or a mixture of ahydrocarbon and a polar organic compound as diluent. Alternatively, amultifunctional polymerization initiator can be prepared in a two-stepprocess by reacting the organomonolithium compounded with a conjugateddiene or monovinyl aromatic compound additive and then adding themultivinyl aromatic compound. Any of the conjugated dienes or monovinylaromatic compounds described can be employed. The ratio of conjugateddiene or monovinyl aromatic compound additive employed preferably shouldbe in the range of about 2 to 15 moles of polymerizable compound permole of organolithium compound. The amount of multivinylaromaticcompound employed preferably should be in the range of about 0.05 to 2moles per mole of organomonolithium compound.

Exemplary multivinyl aromatic compounds include 1,2-divinylbenzene,1,3-divinylbenzene, 1,4-divinylbenzene, 1,2,4-trivinylbenzene,1,3-divinylnaphthalene, 1,8-divinylnaphthalene,1,3,5-trivinylnaphthalene, 2,4-divinylbiphenyl, 3,5,4'-trivinylbiphenyl,m-diisopropenyl benzene, p-diisopropenyl benzene,1,3-divinyl-4,5,8-tributylnaphthalene, and the like. Divinyl aromatichydrocarbons containing up to 18 carbon atoms per molecule arepreferred, particularly divinylbenzene as either the ortho, meta, orpara isomer, and commercial divinylbenzene, which is a mixture of thethree isomers, and other compounds such as the ethylstyrenes, also isquite satisfactory.

Other types of multifunctional initiators can be employed such as thoseprepared by contacting a sec- or tert-organomonolithium compounded with1,3-butadiene, on a ratio of such as about 2 to 4 moles oforganomonolithium compound per mole of 1,3-butadiene, in the absence ofadded polar material in this instance, with the contacting preferablybeing conducted in an inert hydrocarbon diluent, though contactingwithout the diluent can be employed if desired.

Alternatively, specific organolithium compounds can be employed asinitiators, if desired, in the preparation of polymers in accordancewith the present invention. These can be represented by R (Li)_(x)wherein R represents a hydrocarbyl radical of such as 1 to 20 carbonatoms per R group, and x is an integer 1 to 4. Exemplary organolithiumcompounds are methyllithium, isopropyllithium, n-butyllithium,sec-butyllithium, tert-octyllithium, n-decyllithium, phenyllithium,1-naphthyllithium, 4-butylphenyllithium, p-tolyllithium,4-phenylbutyllithium, cyclohexyllithium, 4-butylcyclohexyllithium,4-cyclohexylbutyllithium, dilithiomethane, 1,4-dilithiobutane,1,10-dilithiodecane, 1,20-dilithioeicosane, 1,4-dilithiocyclohexane,1,4-dilithio-2-butane, 1,8-dilithio-3-decene,1,2-dilithio-1,8-diphenyloctane, 1,4-dilithiobenzene,1,4-dilithionaphthalene, 9,10-dilithioanthracene,1,2-dilithio-1,2-diphenylethane, 1,3,5-trilithiopentane,1,5,15-trilithioeicosane, 1,3,5-trilithiocyclohexane,1,3,5,8-tetralithiodecane, 1,5,10,20-tetralithioeicosane,1,2,4,6-tetralithiocyclohexane, 4,4'-dilithiobiphenyl, and the like.

The modifiers which can be employed in the synthesis of polydieneshaving high vinyl contents in accordance with this invention have one ofthe following structural formulae: ##STR4## wherein n represents aninteger within the range of 3 to 6, and wherein R, R¹, and R² can be thesame or different and represent alkyl groups containing from 1 to 10carbon atoms, aryl groups containing from 6 to 10 carbon atoms, orhydrogen atoms.

In these compounds R, R¹, and R² will normally contain from 1 to 6carbon atoms with those containing from 1 to 4 carbon atoms being morecommon. Typically R will represent an alkyl group. As a general rule, nwill represent the integer 3 or 4. More commonly n will represent theinteger 3. In most cases the modifier will be of structural formula (i),(ii), (iii), or (iv). The most preferred types of modifier are alkyltetrahydrofurfuryl ethers such as methyltetrahydrofurfuryl ether,ethyltetrahydrofurfuryl ether, propyltetrahydrofurfuryl ether, andbutyltetrahydrofurfuryl ether.

The modifier being utilized can be introduced into the polymerizationzone being utilized in any manner. In one embodiment, it can be reactedwith the organometallic compound with the reaction mixture therefrombeing introduced into the polymerization zone as the initiator. Inanother embodiment, the modifier can be introduced into thepolymerization zone directly without first being reacted with theorganometallic compound being utilized as the initiator. In other words,the modifiers can be introduced into the polymerization zone in the formof a reaction mixture with the organometallic initiator or they can beintroduced into the polymerization zone separately.

The amount of modifier needed will vary greatly with the vinyl contentwhich is desired for the polymer being synthesized. For instance,polymers with only slightly increased vinyl contents can be prepared byutilizing as little as 0.1 moles of the modifier per mole of metal inthe organometallic initiator being utilized. If polymers having veryhigh vinyl contents are desired, then large quantities of the modifiercan be used. However, normally there will be no reason to employ morethan about 40 moles of the modifier per mole of metal in theorganometallic initiator system employed. In most cases from about 0.25to about 15 moles of the modifier will be employed per mole of metal inthe organometallic initiator system utilized. Preferably from about 0.5to 10 moles of the modifier will be utilized per mole of lithium withfrom about 1 to 5 moles of the modifier per mole of lithium being mostpreferred.

The polymerization temperature utilized can vary over a broad range offrom about -20° C. to about 150° C. In most cases a temperature withinthe range of about 30° C. to about 125° C. will be utilized. Thepressure used will normally be sufficient to maintain a substantiallyliquid phase under the conditions of the polymerization reaction.

The polymerization is conducted for a length of time sufficient topermit substantially complete polymerization of monomers. In otherwords, the polymerization is normally carried out until high conversionsare attained. The polymerization can then be terminated using a standardtechnique. The polymerization can be terminated with a conventionalnoncoupling type of terminator, such as water, an acid, a lower alcohol,and the like or with a coupling agent.

Coupling agents can be used in order to improve the cold flowcharacteristics of the rubber and rolling resistance of tires madetherefrom. It also leads to better processability and other beneficialproperties. A wide variety of compounds suitable for such purposes canbe employed. Some representative examples of suitable coupling agentsinclude: multivinylaromatic compounds, multiepoxides, multiisocyanates,multiimines, multialdehydes, multiketones, multihalides,multianhydrides, multiesters which are the esters of polyalcohols withmonocarboxylic acids, and the diesters which are esters of monohydricalcohols with dicarboxylic acids, and the like.

Examples of suitable multivinylaromatic compounds includedivinylbenzene, 1,2,4-trivinylbenzene, 1,3-divinylnaphthalene,1,8-divinylnaphthalene, 1,3,5-trivinylnaphthalene, 2,4-divinylbiphenyl,and the like. The divinylaromatic hydrocarbons are preferred,particularly divinylbenzene in either its ortho, meta, or para isomer.Commercial divinylbenzene which is a mixture of the three isomers andother compounds is quite satisfactory.

While any multiepoxide can be used, we prefer those which are liquidsince they are more readily handled and form a relatively small nucleusfor the radial polymer. Especially preferred among the multiepoxides arethe epoxidized hydrocarbon polymers such as epoxidized liquidpolybutadienes and the epoxidized vegetable oils such as epoxidizedsoybean oil and epoxidized linseed oil. Other epoxy compounds as1,2,5,6,9,10-triepoxydecane, and the like, also can be used.

Examples of suitable multiisocyanates includebenzene-1,2,4-triisocyanate, naphthalene-1,2,5,7-tetraisocyanate, andthe like. Especially suitable is a commercially available product knownas PAPI-1, a polyarylpolyisocyanate having an average of 3 isocyanategroups per molecule and an average molecular weight of about 380. Such acompound can be visualized as a series of isocyanate-substituted benzenerings joined through methylene linkages.

The multiimines, which are also known as multiaziridinyl compounds,preferably are those containing 3 or more aziridine rings per molecule.Examples of such compounds include the triaziridinyl phosphine oxides orsulfides such as tri(1-ariridinyl)phosphine oxide,tri(2-methyl-1-ariridinyl)phosphine oxide,tri(2-ethyl-3-decyl-1-ariridinyl)phosphine sulfide, and the like.

The multialdehydes are represented by compounds such as1,4,7-naphthalene tricarboxyaldehyde, 1,7,9-anthracenetricarboxyaldehyde, 1,1,5-pentane tricarboxyaldehyde, and similarmultialdehyde containing aliphatic and aromatic compounds. Themultiketones can be represented by compounds such as1,4,9,10-anthraceneterone, 2,3-diacetonylcyclohexanone, and the like.Examples of the multianhydrides include pyromellitic dianhydride,styrene-maleic anhydride copolymers, and the like. Examples of themultiesters include diethyladipate, triethylcitrate,1,3,5-tricarbethoxybenzene, and the like.

The preferred multihalides are silicon tetrahalides, such as silicontetrachloride, silicon tetrabromide, and silicon tetraiodide, and thetrihalosilanes such as trifluorosilane, trichlorosilane,trichloroethylsilane, tribromobenzylsilane, and the like. Also preferredare the multihalogen-substituted hydrocarbons, such as1,3,5-tri(bromomethyl)benzene, 2,4,6,9-tetrachloro-3,7-decadiene, andthe like, in which the halogen is attached to a carbon atom which isalpha to an activating group such as an ether linkage, a carbonyl group,or a carbon-to-carbon double bond. Substituents inert with respect tolithium atoms in the terminally reactive polymer can also be present inthe active halogen-containing compounds. Alternatively, other suitablereactive groups different from the halogen as described above can bepresent.

Examples of compounds containing more than one type of functional groupinclude 1,3-dichloro-2-propanone, 2,2-dibromo-3-decanone,3,5,5-trifluoro-4-octanone, 2,4-dibromo-3-pentanone,1,2,4,5-diepoxy-3-pentanone, 1,2,4,5-diepoxy-3-hexanone,1,2,11,12-diepoxy-8-pentadecanone, 1,3,18,19-diepoxy-7,14-eicosanedione,and the like.

In addition to the silicon multihalides as described hereinabove, othermetal multihalides, particularly those of tin, lead, or germanium, alsocan be readily employed as coupling and branching agents. Difunctionalcounterparts of these agents also can be employed, whereby a linearpolymer rather than a branched polymer results.

Broadly, and exemplarily, a range of about 0.01 to 4.5 milliequivalentsof coupling agent are employed per 100 grams of monomer, presentlypreferred about 0.01 to 1.5 to obtain the desired Mooney viscosity. Thelarger quantities tend to result in production of polymers containingterminally reactive groups or insufficient coupling. One equivalent oftreating agent per equivalent of lithium is considered an optimum amountfor maximum branching, if this result is desired in the production line.The coupling agent can be added in hydrocarbon solution, e.g., incyclohexane, to the polymerization admixture in the final reactor withsuitable mixing for distribution and reaction.

Polymers which are made by utilizing the modifiers of this invention insolution polymerizations can be recovered utilizing conventionaltechniques. In many cases it will be desirable to destroy residualcarbon-lithium bonds which may be present in the polymer solution and torecover the synthetic polymer produced. It may also be desirable to addadditional antioxidants to the polymer solution in order to furtherprotect the polydiene produced from potentially deleterious effects ofcontact with oxygen. The polymer made can be precipitated from thepolymer solution and any remaining lithium moieties can be inactivatedby the addition of lower alcohols, such as isopropyl alcohol, to thepolymer solution. The polydiene can be recovered from the solvent andresidue by means such as decantation, filtration, centrification, andthe like. Steam stripping can also be utilized in order to removevolatile organic compounds.

This invention is illustrated by the following examples which are merelyfor the purpose of illustration and are not to be regarded as limitingthe scope of the invention or the manner in which it can be practiced.Unless specifically indicated otherwise, parts and percentages are givenby weight.

EXAMPLE 1

In this experiment polyisoprene having a high 3,4-microstructure wassynthesized using ethyl tetrahydrofurfuryl ether as the modifier. In theprocedure used 1,500 grams of a silica/molecular sieve/aluminum driedpremix containing 19.4 percent isoprene in hexane was charged into a onegallon (3.8 liters) reactor. After the scavenger level of 2.9 ppm, asdetermined, 0.64 ml of neat ETE (ethyl tetrahydrofurfuryl ether; 7.2M)and 1.65 ml of a 0.75M solution of n-butyl lithium (in hexane; 1.3 mlfor initiation and 0.35 ml for scavenging the premix) was added to thereactor. The molar ratio of modifier/n-butyl lithium (n-BuLi) was 5. Thepolymerization was allowed to proceed at 70° C. for 1 hour. Analysis ofthe residual monomers contained in the polymerization mixture by gaschromatograph indicated that the polymerization was 96.5% complete atthis time. The polymerization was continued for another 30 minutes toassure 100% conversion. Then, 5 ml of 1M ethanol solution (in hexane)was added to the reactor to shortstop the polymerization and polymer wasremoved from the reactor and stabilized with 1 phm of antioxidant. Afterevaporating hexane, the resulting polymer was dried in a vacuum oven at50° C. The polyisoprene produced was determined to have a glasstransition temperature (Tg) at -9° C. It was determined to have amicrostructure which contained 31% 1,4-polyisoprene units, 64%3,4-polybutadiene units and 6% 1,2-polyisoprene units.

EXAMPLES 2-5

The procedure described in Example 1 was utilized in these examplesexcept that the ETE/n-BuLi ratios were changed from 5 to 0.5-3. The Tg'sand microstructures of the resulting polyisoprenes are listed in TableI.

                  TABLE I                                                         ______________________________________                                        Polyisoprenes Prepared Via ETE/N-BuLi                                                 ETE/n-                                                                Example BuLi     PZN*    Tg   Microstructure                                  No.     Ratio    Temp.   (°C.)                                                                       1,4-PI                                                                              3,4-PI                                                                              1,2-PI                              ______________________________________                                        1       5.0      70° C.                                                                         -9   31    64    5                                   2       3.0      70° C.                                                                         -15  37    57    6                                   3       2.0      70° C.                                                                         -23  41    52    7                                   4       1.0      70° C.                                                                         -38  60    37    3                                   5       0.5      70° C.                                                                         -53  81    19    0                                   6       5.0      60° C.                                                                         0    24    66    10                                  ______________________________________                                         *PZN Temp. = Polymerization Temperature                                  

EXAMPLE 6

The procedure described in Example 1 was utilized in this example exceptthat the polymerization temperature was changed from 70° C. to 60° C.The polyisoprene produced was determined to have a Tg at 0° C. It wasdetermined to have a microstructure which contained 24% 1,4-polyisopreneunits, 66% 3,4-polybutadiene units and 11% 1,2-polyisoprene units.

EXAMPLES 7-11

The procedure described in Example 1 was utilized in these examplesexcept that MTE (methyl tetrahydrofurfuryl ether) was used as themodifier. The TG's of the polyisoprenes produced along with theMTE/n-BuLi ratios utilized are tabulated in Table II.

                  TABLE II                                                        ______________________________________                                        Polyisoprenes Prepared Via MTE/n-BuLi                                                 MTE/n-                                                                Example BuLi     PZN     Tg   Microstructure                                  No.     Ratio    Temp.   (°C.)                                                                       1,4-PI                                                                              3,4-PI                                                                              1,2-PI                              ______________________________________                                        7       1.0      70° C.                                                                         -39  62    37    1                                   8       2.0      70° C.                                                                         -26  48    49    3                                   9       3.0      70° C.                                                                         -19  42    54    4                                   10      5.0      70° C.                                                                         -14  36    58    6                                   11      10.0     70° C.                                                                         -7   30    63    7                                   ______________________________________                                    

EXAMPLES 12-16

The procedure described in Example 1 was utilized in these examplesexcept that BTE (butyl tetrahydrofurfuryl ether) was used as themodifier. The Tg's of the polyisoprenes produced along with theBTE/n-BuLi ratios utilized are tabulated in Table III.

                  TABLE III                                                       ______________________________________                                        Polyisoprenes Prepared Via BTE/n-BuLi                                                 BTE/n-                                                                Example BuLi     PZN     Tg   Microstructure                                  No.     Ratio    Temp.   (°C.)                                                                       1,4-PI                                                                              3,4-PI                                                                              1,2-PI                              ______________________________________                                        12      1.0      70° C.                                                                         -35  58    40    2                                   13      2.0      70° C.                                                                         -22  45    52    3                                   14      3.0      70° C.                                                                         -15  39    57    4                                   15      5.0      70° C.                                                                         -9   33    62    5                                   16      10.0     70° C.                                                                         -4   29    64    7                                   ______________________________________                                    

EXAMPLES 17-21

The procedure described in Example 1 was utilized in these examplesexcept that MTE (methyl tetrahydrofurfuryl ether) was used as themodifier and a 50/50 mixture of isoprene/1,3-butadiene was used aspremix. The Tg's of the IBR's produced along with the MTE/n-BuLi ratiosutilized are tabulated in Table IV.

                  TABLE IV                                                        ______________________________________                                        50/50 Isoprene-Butadiene Copolymers                                           Prepared Via MTE/n-BuLi at 70° C.                                      MTE/n-              Microstructure (%)                                        Example BuLi     Tg     1,2- 1,4-  1,2- 3,4- 1,4-                             No.     Ratio    (°C.)                                                                         PBd  PBd   PI   PI   PI                               ______________________________________                                        17      1.0      -48    24   27    ND   27   22                               18      2.0      -39    28   23    2    31   16                               19      3.0      -37    31   22    2    31   14                               20      5.0      -32    32   19    4    34   11                               21      10.0     -30    32   19    5    34   10                               ______________________________________                                    

EXAMPLES 22-25

The procedure described in Example 1 was utilized in these examplesexcept a 20/80 mixture of styrene/1,3-butadiene was used as the premix.The Tg's of the SBR's produced, the ETE/n-BuLi ratios utilized and theirmicrostructures are tabulated in Table V. The ozonolysis data indicatedthat the styrene was randomly distributed in the resulting SBR chains.

                  TABLE V                                                         ______________________________________                                        20/80 Styrene-Butadiene Copolymers                                            Prepared Via ETE/n-BuLi                                                               ETE/n-                                                                Example BuLi     Tg     Microstructure (%)                                    No.     Ratio    (°C.)                                                                         1,2-PBd 1,4-PBd                                                                              Styrene*                               ______________________________________                                        22      1.0      -40    43      36     21                                     23      2.0      -30    52      28     20                                     24      3.0      -28    53      28     19                                     25      5.0      -24    55      26     19                                     ______________________________________                                         *Random                                                                  

EXAMPLES 26-27

The procedure described in Example 1 was utilized in these examplesexcept a 10/90 mixture of styrene/1,3-butadiene was used as the premix.The Tg's of the SBR's produced, the ETE/n-BuLi ratios utilized and theirmicrostructures are tabulated in Table VI. The ozonolysis data indicatedthat the styrene was randomly distributed in the resulting SBR chains.

                  TABLE VI                                                        ______________________________________                                        10/90 Styrene-Butadiene Copolymers                                            Prepared Via ETE/n-BuLi                                                               ETE/n-                                                                Example BuLi     Tg     Microstructure (%)                                    No.     Ratio    (°C.)                                                                         1,2-PBd 1,4-PBd                                                                              Styrene*                               ______________________________________                                        26      1.0      -45    51      38     11                                     27      2.0      -37    58      33      9                                     ______________________________________                                         *Random                                                                  

EXAMPLES 28-29

The procedures described in Example 1 was utilized in these examplesexcept a 10/90 mixture of styrene/1,3-butadiene was used as the premixand MTE (methyl tetrahydrofurfuryl ether) was used as the modifier. TheTg's of the SBR's produced along with the MTE/n-BuLi ratios utilized arelisted in table VII.

                  TABLE VII                                                       ______________________________________                                        10/90 Styrene-Butadiene Copolymers                                            Prepared Via MTE/n-BuLi                                                               MTE/n-                                                                Example BuLi     Tg     Microstructure (%)                                    No.     Ratio    (°C.)                                                                         1,2-PBd 1,4-PBd                                                                              Styrene*                               ______________________________________                                        28      1.0      -54    41      48     11                                     29      2.0      -44    49      41     10                                     ______________________________________                                         *Random                                                                  

EXAMPLES 30-33

The procedure described in Example 1 was utilized in these examplesexcept that the polymerization temperature was changed from 70° C. to60° C. and butadiene was used as the premix. The Tg's, the ETE/n-BuLiratios and the microstructures of the resulting polybutadienes aretabulated in Table VIII.

                  TABLE VIII                                                      ______________________________________                                        Polybutadienes Prepared Via ETE/n-BuLi                                                  ETE/n-                                                              Example   BuLi     Tg       Microstructure (%)                                No.       Ratio    (°C.)                                                                           1,2-PBd                                                                              1,4-PBd                                    ______________________________________                                        30        2.0      -41      71     29                                         31        3.0      -39      76     24                                         32        5.0      -36      76     24                                         33        10.0     -34      78     22                                         34        10.0     -30      80     20                                         ______________________________________                                    

EXAMPLE 34

The procedure described in Example 1 was utilized in this example exceptthat the polymerization temperature was changed from 70° C. to 60° C.and butadiene was used as the premix. The ETE/n-BuLi ratio was changedfrom 5 to 10. The polybutadiene produced was determined to have a Tg at-30° C. It was determined to have a microstructure which contain 80%1,2-polybutadiene units and 20% 1,4-polybutadiene units.

EXAMPLES 35-39

The procedure described in Example 1 was utilized in these examplesexcept that butadiene was used as the premix, MTE (methyltetrahydrofurfuryl ether) was used as the modifier and polymerizationwas performed at 60° C. The Tg's of the polybutadienes produced alongwith the MTE/n-BuLi ratios utilized are listed in Table IX.

                  TABLE IX                                                        ______________________________________                                        Polybutadienes Prepared Via MTE/n-BuLi                                                  ETE/n-                                                              Example   BuLi     Tg       Microstructure (%)                                No.       Ratio    (°C.)                                                                           1,2-PBd                                                                              1,4-PBd                                    ______________________________________                                        35        1.0      -53      58     42                                         36        2.0      -52      60     40                                         37        3.0      -45      66     34                                         38        5.0      -41      70     30                                         39        10.0     -40      70     30                                         ______________________________________                                    

While certain representative embodiments and details have been shown forthe purpose of illustrating the subject invention, it will be apparentto those skilled in this art that various changes and modifications canbe made therein without departing from the scope of the subjectinvention.

What is claimed is:
 1. A process for the synthesis of a rubbery polymerwhich comprises copolymerizing styrene and isoprene in an inert organicsolvent at a temperature which is within the range of about 30° C. toabout 125° C. in the presence of a catalyst system which is comprised of(a) an organolithium initiator and (b) an alkyl tetrahydrofurfuryl ethermodifier, wherein the alkyl group in the alkyl tetrahydrofurfuryl ethercontains from 1 to 10 carbon atoms.
 2. A process as specified in claim 1wherein the molar ratio of the alkyl tetrahydrofurfuryl ether modifierto the organolithium initiator is within the range of 0.25 to about 15.3. A process as specified in claim 2 wherein the alkyltetrahydrofurfuryl ether modifier is selected form the group consistingof methyl tetrahydrofurfuryl ether, ethyl tetrahydrofurfuryl ether,propyl tetrahydrofurfuryl ether, and butyl tetrahydrofurfuryl ether. 4.A process as specified in claim 3 wherein from about 0.01 phm to 0.1 ofthe organolithium initiator is present.
 5. A process as specified inclaim 4 wherein the organolithium initiator is an organomonolithiumcompound.
 6. A process as specified in claim 5 wherein the molar ratioof the alkyl tetrahydrofurfuryl ether modifier to the organolithiuminitiator is within the range of about 0.5 to about
 10. 7. A process forthe synthesis of a rubbery polymer which comprises terpolymerizing1,3-butadiene, isoprene, and styrene in an inert organic solvent at atemperature which is within the range of about 30° C. to about 125° C.in the presence of a catalyst system which is comprised of (a) anorganolithium initiator and (b) an alkyl tetrahydrofurfuryl ethermodifier, wherein the alkyl group in the alkyl tetrahydrofurfuryl ethercontains from 1 to 10 carbon atoms.
 8. A process as specified in claim 7wherein the molar ratio of the alkyl tetrahydrofurfuryl ether modifierto the organolithium initiator is within the range of 0.25 to about 15.9. A process as specified in claim 8 wherein the alkyltetrahydrofurfuryl ether modifier is selected from the group consistingof methyl tetrahydrofurfuryl ether, ethyl tetrahydrofurfuryl ether,propyl tetrahydrofurfuryl ether, and butyl tetrahydrofurfuryl ether. 10.A process as specified in claim 9 wherein from about 0.01 phm to 0.1 ofthe organolithium initiator is present.
 11. A process as specified inclaim 10 wherein the organolithium initiator is an organomonolithiumcompound.
 12. A process as specified in claim 11 wherein the molar ratioof the alkyl tetrahydrofurfuryl ether modifier to the organolithiuminitiator is within the range of about 0.5 to about
 10. 13. A processfor the synthesis of a rubbery polyisoprene polymer which comprisespolymerizing isoprene monomer into polyisoprene having a high level of3,4-microstructure in an inert organic solvent at a temperature which iswithin the range of about 30° C. to about 125° C. in the presence of acatalyst stem which is comprised of (a) an organolithium initiator and(b) an alkyl tetrahydrofurfuryl ether modifier, wherein the alkyl groupin the alkyl tetrahydrofurfuryl ether contains from 1 to 10 carbonatoms.
 14. A process as specified in claim 13 wherein the molar ratio ofthe alkyl tetrahydrofurfuryl ether modifier to the organolithiuminitiator is within the range of 0.25 to about
 15. 15. A process asspecified in claim 14 wherein the alkyl tetrahydrofurfuryl ethermodifier is selected from the group consisting of methyltetrahydrofurfuryl ether, ethyl tetrahydrofurfuryl ether, propyltetrahydrofurfuryl ether, and butyl tetrahydrofurfuryl ether.
 16. Aprocess as specified in claim 15 wherein from about 0.01 phm to 0.1 ofthe organolithium initiator is present.
 17. A process as specified inclaim 16 wherein the organolithium initiator is an organomonolithiumcompound.
 18. A process as specified in claim 17 wherein the molar ratioof the alkyl tetrahydrofurfuryl ether modifier to the organolithiuminitiator is within the range of about 0.5 to about
 10. 19. A process asspecified in claim 18 wherein the alkyl tetrahydrofurfuryl ethermodifier is methyl tetrahydrofurfuryl ether.
 20. A process as specifiedin claim 18 wherein the inert organic solvent is hexane.